CHAPTER XVII. 



THE BESPIBATOBY TBACT. 



BY BENJAMIN F. WESTBROOK, M.D., 



Lecturer on Anatomy and Pathological Anatomy at the Long Island College Hospital, 



Brooklyn, N. Y. 



THE respiratory tract includes the nares and, perhaps, the 

 pharynx, but as the latter is more commonly associated with 

 the function of deglutition, and the former contain in their 

 tipper portions the organs of one of the special senses, they 

 have been assigned to other portions of this work. This chap- 

 ter is devoted exclusively to the consideration of those parts 

 which are concerned in the respiratory process. As the pleura 

 forms a part of the lung, and facilitates the movements of 

 breathing, its structure may properly be described under this 

 section. 



The air-tubes are in general made up of three layers : an 

 outer of connective tissue and elastic fibres ; a middle, muscu- 

 lar and cartilaginous; and an inner of mucous membrane. 

 Their structure is more complex in the upper, and simpler in 

 the lower portions of the respiratory passages. 



The larynx. The muscles of the larynx are of the striped 

 or voluntary variety. 



The ligaments and membranes are composed of yellow elas- 

 tic fibres with some white fibrous tissue. Their structure can be 

 easily demonstrated by the process of teasing or by employing 

 the reagents ordinarily used for this class of tissues. The la- 

 teral thyro-hyoid and the inferior thyro-arytenoid ligaments 

 have the following peculiarities of structure : the lateral thyro- 

 hyoid ligament usually encloses a small piece of hyaline carti- 

 lage about the size and shape of a large grain of wheat. It 

 is known as the cartilago triticea. In adult males it is usually 

 calcified. It may be incorporated either with the cornu of the 

 hyoid bone or with the superior cornu of the thyroid cartilage. 





